A bush bearing as a sliding bearing has advantages in that, as compared with a rolling bearing, the bush bearing is low-priced, and the amount of noise generated is low, so that it excels in the low noise characteristic. Because of such advantages, the bush bearings are used in numerous fields including compressors of automobiles and the like.
The bush bearing is normally press fitted in a hole of a housing, is secured at its outer peripheral surface to the housing, and is adapted to rotatably support at its inner peripheral surface a shaft. To facilitate the press fitting into the housing hole, a tapered surface is formed at an outer peripheral surface on the end face side of the bush bearing.
Incidentally, if a cutting tool (single point tool) is merely abutted against the outer peripheral surface on the end face side of the bush bearing to shave it off so as to form such a tapered surface, there is a possibility that very small burrs are produced on that outer peripheral surface. At the time of the press fitting of the bush bearing into the housing hole, these burrs can fall off and remain in the housing hole as dust (e.g., metal powder dust). This dust can enter between the inner peripheral surface of the bush bearing and the shaft, making it impossible to ensure smooth rotation of the shaft. In addition, particularly in an aluminum-made housing, there is a possibility that the inner peripheral surface of the housing defining the hole is shaved by the burrs at the time of the press fitting of the bush bearing into the housing hole, and aluminum chips are produced. These aluminum chips can enter between the inner peripheral surface of the bush bearing and the shaft, making it impossible to ensure smooth rotation of the shaft.
Furthermore, if the wall thickness on the end face side of the bush bearing becomes extremely small owing to the tapered surface formed, the end face side of the bush bearing becomes easily deformed in the press fitting into the housing hole, making it impossible to assure the roundness of the inner peripheral surface of the bush bearing. Meanwhile, if the tapered surface is formed so as to enlarge the wall thickness on the end face side of the bush bearing in order to avoid this, the positioning and fixation of the bush bearing with respect to the housing hole prior to the press fitting into the housing hole become difficult; moreover, the guiding action based on the tapered surface in the press fitting into the housing hole is practically lost, possibly crushing the end face side of the bush bearing or unnecessarily enlarging the diameter of the open end of the housing hole.